python-gpiozero/docs/notes.md

Notes

1. BCM pin numbering

   This library uses BCM pin numbering for the GPIO pins, as opposed to BOARD. Unlike the RPi.GPIO library, it is not configurable.

   Any pin marked GPIO can be used for generic components.

   The BCM pin layout is as follows:

   3V3	5V
   GPIO2	5V
   GPIO3	GND
   GPIO4	GPIO14
   GND	GPIO15
   GPIO17	GPIO18
   GPIO27	GND
   GPIO22	GPIO23
   3V3	GPIO24
   GPIO10	GND
   GPIO9	GPIO25
   GPIO11	GPIO8
   GND	GPIO7
   DNC	DNC
   GPIO5	GND
   GPIO6	GPIO12
   GPIO13	GND
   GPIO19	GPIO16
   GPIO26	GPIO20
   GND	GPIO21

   • GND = Ground
   • 3V3 = 3.3 Volts
   • 5V = 5 Volts
   • DNC = Do not connect (special use pins)

2. Wiring

   All components must be wired up correctly before using with this library.

3. Keep your program alive with signal.pause

   The following program looks like it should turn an LED on:

   from gpiozero import led
   
   led = LED(2)
   
   led.on()
   

   And it does, if you're using the Python shell, IPython shell or IDLE shell, but if you saved this program as a Python file and ran it, it would flash on for a moment then the program would end and it would turn off.

   The following file includes an intentional pause to keep the program alive:

   from gpiozero import LED
   from signal import pause
   
   led = LED(2)
   
   led.on()
   
   pause()
   

   Now running the program will stay running, leaving the LED on, until it is forced to quit.

   Similarly, when setting up callbacks on button presses or other input devices, the program needs to be running for the events to be detected:

   from gpiozero import Button
   from signal import pause
   
   button = Button(2)
   
   button.when_pressed = lambda: print("Button was pressed!")
   
   pause()